In the petroleum industry, several processes use water in the refinery process for treatment or as steam in large quantities. This causes a huge water usage load on a given refinery. The usage of this water is different than traditional municipal waste water. This results in the water as well to have a different composition and contain different amount of particulates. In several processes the waste water can be reused for additional processes. This is because the water does not need to be clean on the drinkable scale, but can contains containment’s such as hydrocarbons depending on the additional processes which it can be used for. As a result the water should be kept separate completely from other water streams. Combining the streams would increase the load on the waste water treatment facilities, not be efficient, and cause refinery costs to increase.

In a refinery the processes as the water comes in contact with petroleum fractions, it becomes highly polluted. This includes containment’s such as aromatics, heteroatoms, dissolved gas, acidic acid, particulates, and dissolved solids. In municipal water the content of these containment’s are much less. This results in the traditional waste water treatment not to be designed to remove these pollutants since the content is usually already to acceptable levels, or not designed to remove the pollutants to the scale at which the waste water would need. This is why a separate treatment plant is needed to accurately and efficiently use the water and so it meets acceptable levels.